Method of recovering gold and silver



Aug. 11, 1931. s. A. GILES METHOD OF RECOVERING GOLD AND SILVER FiledNov. 22, 1929 W5 e Z 7. G

Patented Aug. 11 1931 UNITED STATES.

STELLE A. GILES, F HUTCHINSON, KANSAS METHOD OF RECOVERING GOLD ANDSILVER Application filed November 22, 1929. Serial no. 4oa,1ae.

This invention relates to gold and silver recovery processes and has foran ob ect to provide a process which will effect the removal of limitingelements that present 5 ordinary methods of recovery such as thecyanide, chlorine or amalgamation process from being effective inrecovering gold and silver from low grade ores.

A further object is to produce a process which will loosen the gold fromthe gangue in a simple inexpensive manner and without the use ofexpensive equipment.

The method which is the subject matter of the present invention appliesgenerally to the 'recovery 'of that type of gold known as colloidalgold, that is, floating gold or flake gold, this type of gold beinghighly elusive and too tightly sealed in the gangue or ore containing itto be recovered by the m usual gold recovery methods. The gangue ofwaste matter in which colloidal gold is sealed usually consists ofsilica, sulphur, carbon, hosphorus, nitrogen, arsenic and the like anthese materials are known as the limiting elements which have hithertorendered the recovery of the old from low grade ores such as shales anthe like which cover a great portion of the surface of the earth,unprofitable and impractical.

39 The present, invention provides a method of removing some of theselimiting elements by oxidation and simultaneously loosening or crackingthe gangue to free the gold flakes for recovery.

I have found that colloidal gold can be profitably recovered fromvarious low grade ores, particularly shales, sands, etc. and for thepurpose of the present invention, the recovery of colloidal gold fromshales laid 40 down in salt Water such as the well known Benton shalesfound in Kansas and the red shales found 'in the Western States of theUnited States, will be described.

In carrying out the invention a specific example will be given it beingunderstood that modifications may be resorted to within the scope of theappended claim to accomodate the process to the various grades or typesof material to be treated. To facili- 5 tate a clear understanding ofthe process reference may be had to the accom 'anying drawing in whichthe figure is a ongitudinal sectional view through the apparatus. Incarrying out the invention I first grind or pulverize the colloidal goldbearing shale-'55 to pass through a mesh or a finer mesh. This grindinmay be accomplished in the usual way an by use of the usual a paratus.The finely ground or pulverize shale is then dumped into a hopper 10 andblown 60 intov an oxidizing chamber 11 of a water jacketed furnacebymeans of an air blast admitted through an inlet pipe 12 which iscontrolled by a valve 13. The nozzle of the pipe is directed upwardly tocause the finely pulverized material to be directed upwardly in anarched stream as shown while it passes through the oxidizing chamber 11and into the reducing chamber 14. The material from the pulverizedarched stream in- 7 dicated at 15 gravitates to the bottom 16 of thefurnace and while droppin is subjected to an oxidizing flame as wil nowbe described.

A fuel pipe 17 is conducted into the furnace, the fuel preferably beingoil, gas or any other desired fuel,'the pipe being controlled by a valve18. The nozzle 19 of the pipe is directed upwardly to cause the flame 20to arch upwardly and meet the stream of finely pulverized shale and heatthe latter during its passage through the furnace. The oxygen of the airblast supplies an excess of oxygen in the chamber 11 of the furnace sothat the flame becomes an oxidizingflame and consumes the gaseouslimiting elements such as carbon, sul hur, arsenic, phosphorus and thelike contained in the shale.

This heating step is carefully controlled as to temperature so that atno time will 99 the temperature rise suficiently to cause meltin andformation of a glass-1ike substance. no n as slag, as this would behighly detrimenta to the recover since any fiuxing would cause rescalingof t e gold.

This initial heating step in addition to consuming the limiting elementsalso serves to loosen themicroscopic particles of gold from the gangueof silica, lime, etc. in which it is sealed due to a difference inexpansion. 100

The gold will expand a far greater extent than the gangue under the samedegree of heat and crack open or loosen the gangue.

' It has been found by experiment that a ing the limiting elements havebeen removed stream in the reducing s and have vanished from the shalebeing treated and also the gangue has been loosened from around themicroscopic gold.

The next step-in the process consists of subjecting the pulverized shaleto preferably a reducing flame. In carrying out this step the stream ofulverized material is directed into the reducm chamber 14 of thefurnace, in which there 1s a deficiency of oxygen so that the oxides ofvarious elements which cling to theparticles of old will be removed andthe flakes of old reed. However, in certain grades of s alewhere thecarbon is the greatest limiting feature it is desirable to supply thechamber 14 of the furnace with additional oxygen in order to effect thecomplete remova of the carbon and for this purpose an air inlet pipe 21is conducted into the chamber 14 and is controlled by a valve 22.

Floatin particles carried up through the stack 23 o the furnace arerecovered preferably by means of a spray of water 24 which is directedinto the stack through a valve controlled nozzle 25. The water carriesthese particles as well as the gravitated material in the furnace downalong the S10 ing bottom 16 of the furnace and thence orwardly to aconveyor 26 the latter discharging into a rinder 27. i

n some cases it will be necessar to use mechanical means 28 for removingt e floating particles of ash from the stack gases. This is especiallytrue when sulphur and. arsenic are present. The material gravitatin fromthe arched c amber 14 drops throu h cold water coi 29 which chill andcool t e particles sufliciently to prevent the formation of slag withconsequent rescaling of the old when the material accumulates on theottom 16 of the furnace.

The final step of the process consists of regrindingthe material in therinder 27 e to pass through a 200 mesh or ner mesh,

the material in this condition being known as slime. an of the usualrecovery methods such as ch oride, cyanide or amalgamation for therecovery of the gold therein.

It will be noted that the pulverized ore is maintained in a heatedcondition during its removal from the furnace and during the re rindingstep forrecoveringthe gold. 7

aving ,thus described the invention, I

ing effect of a water-coil near the end of its path through the furnaceto prevent formation of slag and prevent the resealing of the gold,during the chilling step subjecting the ore stream to a reducing flamein which there is a deficiency of 0 gen to-free the flakes of gold'fromthe oxi es-of said limiting elements, removing the product from thefurnace by a water stream to produce a slime or pulp in which the goldis free, and recovering the gold by cyanide, chloride or amalgamationtreatment.

ture.

.STELLE A. GILES. [L- 8.]

This slime is then subjected to '0 arm: a A method of treating colloidalgold bear- In testimony whereof 'I afiix my signa-

